STR: short-term relationship. Conversely, LTR: long-term relationship. You know how you spend one day talking to a Sim and your relationship numbers are 50/10 or some such? That's the STR/LTR.

And w00t for casual woohoos!

I'm sad to say I'm not quite happy with the way that Grant came out -- I can't look at him and immediately recognize him as Grant. (So I could use tips, or even a hand-crafted Sim...!)